drm/amd/display: do not copy invalid CRTC timing info

Since b255ce43, it is possible that the CRTC timing
information for the preferred mode has not yet been
calculated while amdgpu_dm_connector_mode_valid() is running.

In this case use the CRTC timing information of the actual mode.

Fixes: b255ce43 ("drm/amdgpu: don't change mode in amdgpu_dm_connector_mode_valid()")
Closes: https://lore.kernel.org/all/ed09edb167e74167a694f4854102a3de6d2f1433.camel@irl.hu/
Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/4085


Signed-off-by: Gergo Koteles <soyer@irl.hu>
Reviewed-by: Zaeem Mohamed <zaeem.mohamed@amd.com>
Tested-by: Mark Broadworth <mark.broadworth@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 20232192)
Cc: stable@vger.kernel.org